(1) Field of the Invention
The present invention relates to an anvil roll assembly for a rotary die cutting press that is radially adjustable toward and away from the die cutting cylinder of the press.
(2) Description of the Related Art
Prior art rotary die cutting presses are often employed in cutting self-adhesive labels from layered web stock having a label material layer, an adhesive layer, and a backing material layer. The prior art die cutting cylinders employed in the presses for cutting the webs of layered material, and also employed in other similar cutting operations, are generally constructed to suit the particular type of web material employed. The thickness of the web and/or the number of web layers to be cut through must be taken into consideration when determining the clearance between the cutting edges of the die cutting cylinder and the surface of the anvil roll between which the web material is passed. This clearance is determined by the relative spacing between the cutting edges of the die cutting cylinder and the circumferential surfaces of the cutting cylinder's bearer rolls, added to the spacing between the surface of the anvil roll and the circumferential surfaces of the anvil roll's bearer rolls. If the cutting edges of the die cutting cylinder penetrate too far into the layers of the web material, the cutting edges may penetrate the backing layer of the web material causing the backing layer to tear when the cut labels are separated from the backing layer. If, on the other hand, the cutting edges of the die cutting cylinder do not penetrate far enough into the layers of the web material, the depth of the cut will be inadequate to completely penetrate through the label material and the labels will tear when they are separated from the backing material.
One approach to solving the above-described difficulties has been to provide a set of stepped anvil rolls, each cylindrical anvil roll having a different dimensioned outer diameter. The different outer diameters of the anvil rolls will position the anvil roll surfaces at different radial heights relative to the circumferential surfaces of the anvil roll end bearers depending on which anvil roll of the set is assembled on the cutting press. Interchanging the different anvil rolls on the press will adjust the anvil roll surface radially relative to the circumferential surfaces of the anvil roll end bearers, in addition to adjusting the position of the web material relative to the cutting edges of the die cutting cylinder. With a set of stepped anvil rolls, the position of the anvil roll surface relative to the circumferential surfaces of the anvil end bearers and relative to the cutting edges of the die cutting cylinder can be adjusted for web materials of different thicknesses and to compensate for wearing down of the cutting edges of the die cutting cylinder.
However, maintaining a large set of anvil rolls of different outer diameters may not be satisfactory in all situations. Maintaining a large selection of anvil rolls of different outer diameters would be a considerable expense. The manual labor required in replacing the anvil rolls on the press and the down time of the press while such replacements are made also add to the disadvantages of this approach. These shortcomings illustrate the need for an alternate solution to enable adjusting the clearance between an anvil roll surface and the cutting edges of a die cutting cylinder to accommodate the range of conditions encountered in die cutting operations.
In the Reed U.S. Pat. Nos. 4,130,042 and 4,226,150, an assembly is disclosed by which the eccentricities of end bearers of an anvil roll are varied to change the clearance between the anvil roll and cutting cylinder of a press. However, the mechanism disclosed in these patents is relatively complex, and requires that both end bearers be adjusted, thereby introducing the possibility of inaccurate adjustments due to misalignment and clearance variations across the width of the web material.
Furthermore, in related but slightly different applications of rotary presses, web materials are blanked, creased, folded, hinged and scored using rotary dies. Problems similar to those set forth above are encountered in controlling the depth of penetration of the rotary die element in creasing and scoring operations of the press, and in performing creasing and scoring operations on web materials of different thicknesses. In view of the similarities between these operations of the rotary die press and the cutting operation described above, references herein to "cutting" operations should be broadly construed and are intended to be broadly construed to include blanking, creasing, folding, hinging and scoring web materials in addition to other related operations not specifically set forth herein.
What is needed is a novel anvil roll in which the height or radial extension of the cylindrical body portion of the roll, which provides the anvil surface which opposes the cutting edges of a die cutting cylinder, can be varied in relation to the circumference of the end bearers of the anvil roll.